This invention relates to a reciprocating press for shaping or forming simple workpieces such as spheres and the like out of rod parts within a die or mold cooperable with a mating die or mold wherein one of a pair of dies is reciprocated by a crankshaft and the other die of the pair is secured to a frame. The workpiece which is to be shaped or formed is cut off by a shear-off cutter of a feed mechanism which feeds the workpiece to the dies.
Each full turn of a crankshaft causes in a center press of the type known in the art, a molding action, usually when the forward stroke of the sliding carriage carrying the movable die occurs. The extremely large forces occurring at that moment demand a correspondingly large stability of the frame of the press which carries the fixed die. The output of such a press depends only on the speed which governs a cycle of operations, that is the cycle involving the opening and closing of the two dies which form the mold. The operating speed can be practically increased only at the expense of the weight or mass being moved, but there are very narrow limits to a diminution of these weights or masses.
Doubly acting reciprocating presses are known where one mold each is arranged oppositely upon both sides of a crankshaft. For that purpose the already very heavy mounting must be built doubly heavy which leads to an undesired heavy construction.
Accordingly, there exists a need to increase the output of such reciprocating presses, and this is achieved, according to one embodiment of the present invention, by providing two molds with one mold each being arranged side-by-side on both sides of a feed mechanism. The movable dies of the molds are driven by a crankshaft which has crank arms staggered or offset 180.degree. relative to one another and a shear-off knife disposed reciprocatingly between the fixed dies, the shear-off knife providing on both frontal ends a cutting edge and a holding fixture for the reciprocal feeding of workpieces to each of the fixed dies.
The parallel arrangement of two molds side-by-side according to the present invention allows a particularly economical use of the press frame which is exposed to the mold pressure because each full turn of the crankshaft causes two molding cycles. Accordingly, each time only a single molding pressure acts upon the press frame. Therefore, output of a reciprocating press can be doubled while it runs at the same speed, and this can be accomplished practically without enlarging the frame. Thus the frame is better utilized.
According to one embodiment of the present invention, there is provided a feed mechanism common to both molds, such feed mechanism being doubly acting. Thus at the forward stroke, there is effected a cutting off of a workpiece and a feeding of the cut-off workpiece to the fixed die, and at the return stroke, there is effected a cutting-off again of another workpiece, and a feeding of the latter workpiece to the other fixed die.
The side-by-side arrangement of two carriages together with the movable dies causes an excellent equilibration while the identical weights or masses are movable. It is, of course, possible and known in the art to furnish each mold with two or more dies.
According to another embodiment of the present invention, there is provided near each fixed die a separate feeding mechanism with a shear-off knife and a workpiece holding fixture in order to feed the particular die. This latter embodiment has the advantage that both molds may be arranged extremely close to each other, an arrangement which results in a still more economical construction and an improved control of arising forces. It is possible to determine from case to case which one of these independent embodiments is more advantageous in each particular situation.
The movement of one or both feeding mechanisms depends advantageously on the movement of the crankshaft. This dependence may be realized by a cam carried on the crankshaft, such cam mating with one lever arm of a double arm rocking lever, the other lever arm of the double arm rocking lever mating with the carriage in the direction of the feed of the workpiece. It is also possible, for example, to arrange a cone pulley drive upon the main shaft and to regulate the rocker arms by the cam shaft so that the rocker arms move the carriage of the shear-off knives and the support for the separated workpiece each time from one final position into the other final position.
Other features which are considered characteristic of the invention are set forth in the appended claims.
Although the invention is illustrated and described in relationship to specific embodiments, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.